Recovery and purification systems for acrylonitrile and methacrylonitrile obtained by the ammoxidation of propylene or isobutylene are known, see for example U.S. Pat. Nos. 3,433,822; 3,399,120; and 3,535,849. The systems used involve the direct contact of the reactor effluent with an aqueous quenching liquid in a quenching system. In the quenching system, the reactor effluent is usually cooled to a temperature between about 90.degree. to about 230.degree.F.
The gases from the quenching system are then normally conducted to an absorber where the acrylonitrile or methacrylonitrile and water-soluble by-products are absorbed in water. The aqueous solution formed in the absorber is then treated in various distillation columns to obtain the desired product. The total system for recovery and purification may vary widely in the make-up of the individual components. Usually, however, they involve at least four components: one that removes acetonitrile; one that removes hydrogen cyanide; one that dries the acrylonitrile or methacrylonitrile product; and one that recovers the product. Many systems also use an ammonium sulfate recovery component. The particular components in the total recovery and purification system are not critical in the present invention.